The related-art sheet cutter for cutting the sheet using a stationary knife and a movable knife had a structure of cutting the sheet between the stationary knife and the movable knife by pressing and urging the entire movable knife to the stationary knife by means of a pressing welding spring to make the stationary knife and the movable knife mesh with each other while making a tip of a cutting edge part of the movable knife contact with the stationary knife. For example, there are sheet cutters as described in JP-B-8-22517 (refer to patent document 1), JP-B-7-11907U (refer to patent document 2), and JP-B-8-5030 (refer to patent document 3).
In the related-art example as described in JP-B-8-22517 (refer to patent document 1), since the stationary knife or the movable knife is formed in the convex shape, if one tries to form the knife in the optimal shape and accurately, the cost of working is increased, or if one tries to form the knife at low cost, the knife can not be formed in the optimal shape and accurately.
Also, there was a problem that if the cutting edge is not formed in the optimal shape and accurately to produce a gap between both knives, the sheet is plucked, when cut away, to produce unclean cut section, or if there is any interference or the pressing force s too high, a drive load of the movable knife on the motor is increased, and the abrasion of knife is severer.
Thus, the present inventor has offered a sheet cutter comprising a stationary knife including a straight blade part formed like the straight line in the longitudinal direction, a movable knife, including a cutting edge part formed on the slant oppositely to mesh on a meshing plane with the straight blade part of the stationary knife, that can freely move toward or back from the stationary knife, a movable knife pressing member for pressing the movable knife to the stationary knife, and movable knife driver driving the movable knife forward or backward, wherein the movable knife is provided with a protrusion near the cutting edge part on the back of the meshing plane, the movable knife pressing member is provided with a pressing end portion near the straight blade part of the stationary knife, and the pressing end portion presses the protrusion to press the movable knife against the stationary knife in a state where the meshing plane is inclined in a direction where the tip recedes from the opposed surface of the stationary knife, as shown in JP-A-10-315184 (refer to patent document 4).
Patent document 1: JP-B-8-22517
Patent document 2: JP-B-7-11907U
Patent document 3: JP-B-8-5030
Patent document 4: JP-A-10-315184